fix app.* functions & update 'world' test

dev/tests/chunks.lua

@@ -1,4 +1,4 @@
-local util = require("core:tests_util")
+local util = require "core:tests_util"
 util.create_demo_world()
 
 app.set_setting("chunks.load-distance", 3)
@@ -27,3 +27,4 @@ end
 player.delete(pid2)
 
 app.close_world(true)
+app.delete_world("demo")

dev/tests/world.lua

@@ -1,6 +1,7 @@
 -- Create/close/open/close world
 
 -- Open
+app.reconfig_packs({"base"}, {})
 app.new_world("demo", "2019", "core:default")
 assert(world.is_open())
 assert(world.get_generator() == "core:default")
@@ -18,6 +19,9 @@ assert(world.is_open())
 assert(world.get_total_time() > 0.0)
 assert(world.get_seed() == 2019)
 app.tick()
+app.reconfig_packs({}, {"base"})
+app.tick()
 
 -- Close
 app.close_world(true)
+app.delete_world("demo")